This invention relates generally to integrated control systems for producing a blend of substances and more particularly, but not by way of limitation, to control systems, having an automated proppant delivery system, for producing fracturing fluids.
In the oil and gas industry, it is well known that in creating an oil or gas well various fluids or flowable blends need to be prepared for pumping downhole to accomplish different, known purposes. In hydraulically fracturing a selected formation within a well, a fracturing fluid, comprising a selectable combination of substances or materials, needs to be produced and pumped downhole. For example, a liquid gel concentrate might be mixed with selectable ones of several known additives to produce a mixture which is then blended with sand or other particulate material, referred to as a proppant, to produce the fracturing blend which is to be pumped downhole. Such a blend is prepared at the well site, which requires storage facilities for storing the substances to be mixed and blended, equipment for mixing and blending the substances, and equipment for pumping the resultant blend into the well.
The need for such fluids and the equipment for producing and pumping such fluids has been recognized and has, to some degree, been met by individual pieces of equipment which are separately transported to a common site and separately controlled for use collectively in producing and pumping the blend. Mixing and blending equipment are described in U.S. Pat. Application Ser. No. 483,001, Apparatus and Method for Mixing a Plurality of Substances, filed Apr. 6, 1983, now U.S. Pat. No. 4,538,221, and in U.S. Pat. Application Ser. No. 483,031, Apparatus and Method for Mixing a Plurality of Substances, filed Apr. 6, 1983 now U.S. Pat. No. 4,538,222. A proppant conveying system is described in U.S. Pat. No. 4,701,095. These patents and applications, which have been assigned to the assignee of the present invention, disclose equipment which has been in public use for more than one year. These patents and applications are incorporated herein by reference both for the background and prior art disclosures made therein of pertinence to the present invention and for the disclosure of equipment exemplifying the type of individual elements which can be adapted for use in the present invention.
One shortcoming of the aforementioned prior art is that many separate pieces of equipment must be separately transported and assembled together for each fracturing, or other type of fluid preparation and pumping, job. This requires maintaining logs of the individual pieces of equipment to insure that suitable ones will be available when needed. This also requires repeated assembly and disassembly of the separate elements from job to job. Still another shortcoming is that the separate pieces of equipment are separately controlled, often with much manual labor involved in the load manipulation of valves and couplings. Therefore, there is the need for an integrated system in which all necessary materials or substances can be stored, mixed, blended and pumped without the need to individually collect, assemble and disassemble separate pieces of equipment for each fluid producing and pumping job. There is also the need for such an integrated system to be controlled in a uniform or integrated fashion to insure the preparation of a proper blend and to reduce the amount of direct manual labor involved in the manipulation of the equipment. These needs contemplate that the original construction of the overall system is to include a single transportation vehicle so that all of the equipment of the system can be fixed to the vehicle and simultaneously transported by it.
The foregoing needs have become particularly critical for offshore drilling operations where it may be even more inefficient and hazardous to try to assemble on the offshore drilling platform, or to provide with a number of floating vessels, the type of storage, conveying and metering system, with the previously required personal involvement with the equipment, necessary to properly produce and pump a blend into an offshore well. Therefore, there is the particular need for an ocean-going integrated system for controlling the production of a fluid, such as a fracturing fluid.
The need for an integrated control system provides for coordinated control of the overall production and pumping activities and further facilitates remote, automated control of servomechanisms utilized throughout the system in controlling the mixing, blending and pumping of the blended substances. Such integrated control also permits system control from a single location.